This invention relates to a novel process for the preparation of N-substituted imidazolidinones and N-substituted 2-thionimidazolidinones.
N-substituted imidazolidinones and N-substituted 2-thionimidazolidinones have recognized utility as bactericides, central nervous system depressants, plant growth promoters, female fly sterilants, adhesives, textile treating agents, and as monomers for deriving polymers and copolymers.
N-substituted imiadazolidinones can be prepared by several prior art processes. Wright et al., J. Med. Chem., 9, 856 (1966), teach a three-step process for such preparation wherein an aniline, which can be substituted, is reacted with 2-bromoethylamine in the presence of base, such as potassium hydroxide, to prepare an N-phenylethylenediamine. The product is thereafter reacted with potassium cyanate to prepare a 2-anilinoethyl urea, which is thereafter thermolytically cyclized to form the N-substituted imidazolidinone by heating the anilinoethyl urea in an oil bath at about 220.degree. C. This process has significant disadvantages including the use of toxic bromoethylamine, two of the steps produce a salt and the synthesis described requires three steps.
Najer et al., Bull. Soc. Chem. France, 323-8 (1963), teach that N-substituted imidazolidinones may be prepared by the reaction of aziridine with an organic isocyanate to prepare a urea intermediate represented by the formula ##STR1## The urea intermediate is thereafter contacted with six-fold molar excess of sodium iodide in dimethyl carbonate and refluxed for 30 hours to prepare N-substituted imidazolidinones. This process has several disadvantages including the use of highly toxic aziridine as a starting material, the requirement of large amounts of sodium iodide in the second step and long reaction times.
Gulbins et al., Justus Liebigs Ann. Chem., 698, 180 (1966), teach that N-substituted aziridines can be reacted with isocyanates in the presence of lithium chloride or lithium bromide catalysts at elevated temperatures to prepare N-substituted imidazolidinones. A major competing reaction is the trimerization of the isocyanates. The major disadvantages of this process are the use of highly toxic aziridine as a starting material and the comprising trimerization of the isocyanates.
Aelony et al., U.S. Pat. No. 3,876,657; see also J. Heterocyclic Chem., 9, 687 (1972); disclose a three-step process for the preparation of N-substituted imidazolidinones. In the first step an amine is reacted with an acrylic ester to form an adduct. In the second step, the adduct is converted to an aminimide by the reaction of the adduct with a trialkyl hydrazinium halide in the presence of a suitable dehydrohalogenating agent or by reaction of the adduct with an asymmetrical disubstituted hydrazine and a lower alkylene oxide. The tertiary amine monoimides are thermolytically rearranged to prepare the imidazolidinones by heating them at a temperature in excess of 140.degree. C. for a sufficient time. The use of strong bases in the synthesis and the multistep synthesis required are two major disadvantages with this process.
In British Pat. No. 1,065,295, N-substituted imidazolidinones prepared by reacting oxazolidinones with an isocyanate at an elevated temperature and preferably in the presence of a catalyst which is a tertiary amino base or lithium chloride. It is further disclosed that preferred temperatures are between about 120.degree. C. and 180.degree. C. with a reaction time of 4 to 12 hours. The catalysts can be used in amounts such as 1/20 mole per mole of the initial oxazolidinone. The examples demonstrate the use of catalyst amounts varying between about 10 and 33 mole percent based on the moles of oxazolidinone. The major disadvantage of this process is the requirement of a relatively large amount of catalyst.
Unfortunately each of the prior art processes described has one or more disadvantages. The most prevalent is the requirement of large amounts of base to catalyze the reaction. Other major disadvantages are that some of the processes use toxic reactants, some require multistep reaction sequences, and some processes produce salt by-products. Long reaction times are another major disadvantage.
A process which is simple, which does not use base and uses small amounts of catalyst for the reaction is desirable. A process which does not use toxic reactants or produce salt by-products is also desirable.